Ebay is a great place to start your search. Search for Dante cosplay or add Devil may cry 2 to that. (If you do add DMC2, you'll get a lot of DMC 2 items, mostly the games). Several versions of Dante's costume exist, so you'll need to search around for the version you want.

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Don't meddle in the affairs of dragons, for they think you are crunchy and good with ketchup.

DMC1's is really easy. It's a vest with exaggerated points on the bottom, and it cuts above the waist in the back (won't be able to find it, have to make or modify), and buckles in the front. It also has a black collar that he wears standing up. Red pants. Boots with buckles. Underarmor shirt. plain black leather gloves.

Coat color varies between games and art, but it is really simple. It has no extra crap on it, and simple lapels. I found mine on ebay and aside from the sleeves and being a little bit big, it was perfect.